Dendritic cells (DC) represent the most potent antigen presenting cell (APC) for stimulating naove T cells. We administered Flt3L to patients with metastatic colon or lung cancer to expand DC. DC were harvested from patients by leukapheresis, enriched by density centrifugation, loaded with antigen, and infused into the patients as an autologous vaccine. The target antigen employed was a HLA*A0201 restricted synthetic peptide derived from carcinoembryonic antigen (CEA).